This invention relates generally to claw-type drilling heads.
Conventional claw-type drilling heads require the use of a pilot bit, centrally disposed in order to keep the drill head from wandering.
The following patents reflect the state of the art which applicant is aware:
______________________________________ D 225,075 2,855,181 Olsen 2,650,071 Rassieur 3,269,471 Alexander ______________________________________
Olsen teaches the use of a drill bit in which a plurality of stepped cutting edges are provided in order to insure a straight hole.
Rassieur teaches the use of a mining drill comprised of two half-shank sections 8 provided with a hole 15 adapted to receive pins 4 for manipulation of each half-shank.
Alexander teaches the use of a rock drilling bit in which the contour of the cutting edges is such that the bit will be substantially clean or have a chip-free surface for cutting at all times.
Clearly, these prior art patents are not only structurally dissimilar but also functionally inefficient when compared to the instant invention as set forth hereandafter and as claimed.